Presence is generally defined as knowing that a person is available via, for example, a certain device over a particular medium as soon as a user connects to the network. For instance, via presence information, it may be ascertained that the person is available online, and on a connected device with a certain device profile. The user which indicates its presence on the network is termed a presentity. Presence is used to notify a group of watchers in a contact list about the state of person, including availability. When the user changes its presence state, each contact on the contact list is informed about the new presence state of the user. Presence infrastructure is used predominantly with Instant Messaging (IM) or Short Message Service (SMS) on a computer. However, the distinction between computers, personal digital assistants and cellular telephones has been progressively blurring which allows a cross over of functionality between one type of Internet Protocol (IP) device to another.
Radio jamming techniques are sometimes used either to block the use of cellular telephones in certain areas, or to notify a cellular telephone that it is in a restricted area and certain types of communication are not recommended or allowed. Cellular telephone jamming can be a legitimate tool for certain applications. For example, jamming can be used to prevent cellular telephone calls from interrupting a church service or a theater presentation through either blocking or ring restriction. The problem is, even when jamming is used for legitimate purposes, it can still have negative side effects. For example, jamming can prevent reception of emergency cellular telephone calls.
The present invention addresses negative side effects that can result from legitimate jamming such as a caller not knowing the person being called is in the restricted area such as in a theater. Current jamming devices may cause a cellular telephone to switch from ringer to vibrate mode. If the person in the theater receives an incoming cellular telephone call, that person may choose to answer the cellular telephone, but answering the cellular telephone may take time as the person leaves the theater and walks to the lobby. If the caller is unaware that the person is in the restricted area, the caller may hang up before the person receiving the call can answer. Presence can be used to communicate to a potential caller (the watcher) that the person receiving the call (the presentity) is in the restricted area.
Therefore, what is needed is a method of extending the presence system to cellular telephones to overcome negative side effects associated with jamming. More specifically, the present invention provides alternative communications during jamming in a presence system.